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Hammerhead Worm
Bipalium kewense

Most planaria are aquatic, that is, they live in water.  Bipalium kewense is one of the few which live on land.  Originating in the wet forests of southeast Asia, it has spread throughout the world as stowaways in pots of plant specimens.  It eats earthworms and slugs, among other things.  B. kewense has become well established in the gardens of this part of California.

Hammerhead Worm, Bipalium kewenseOne never knows what one might find when turning over an object which has been lying on damp ground.  Is it a worm? a slug? or just a slimy mess?

Hammerhead Worm, Bipalium kewenseBeing negatively phototactic (it likes dark places), it soon begins it unwind as it heads for the nearest shadow.  The head, flattened and wider than the body, is characteristic of planaria in general.

Hammerhead Worm, Bipalium kewenseHere we see a planarian eating an earthworm.  The back part of the planarian is coiled over the part of the earthworm which is being digested.  Flatworms must digest their food outside their bodies.

Hammerhead Worm, Bipalium kewenseThis animal measured at about 25 cm in length.  (Sorry about the archaic inches on the ruler, one uses what is close at hand.)

Hammerhead Worm, Bipalium kewenseLook carefully, and you can see the slime trail left behind by the planarian.  It is similar to trails left by slugs and snails.

UPDATE:  Before 1990, the hammerhead worm was rather rare in this part of southern California.  By the late 1990's they had become very common.  In 2005 I saw them almost daily on walks wet by sprinklers.  Since January, 2006, when I received a request for live specimens, I have not seen a single one.  In addition, earthworms also seem to have disappeared.

[Taxonomy : Classification]
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